Phonolite lava erupting
from Jabal Shalman, a basaltic scoria cone on the Harrat Kishb
lava field of western Saudi Arabia -- The phonolite is most likely post-Neolithic in
age based on the lack of Neolithic monuments commonly developed
on adjacent lava flows. This exceptionally thick flow is 2.5
km long, 1.0 km wide, and 40 m thick. It contains flow ridges
and a coarse blocky surface. The light-colored flow to the left
is an older , thicker (100 m) phonolite which extruded from a
separate scoria cone. Courtesy of John Roobol.